Conventionally, an engine including a common rail or the like that can control a fuel injection timing is known. Patent Document 1 discloses this type of engine.
An engine of Patent Document 1 controls a fuel injection timing depending on the various data. In the following, a configuration of Patent Document 1 will be described with reference to FIG. 6. In Patent Document 1, a standard injection timing map 91 is applied to an engine speed and a fuel injection amount, and thereby the fuel injection timing (standard injection timing) is calculated as the standard. In Patent Document 1, various types of correction amount are added to this standard injection timing, and thereby a final injection timing is calculated.
Here, in an area having low atmospheric pressure such as highlands, the stability of ignition is decreased due to pressure drop within a cylinder (see highlands/steady of FIG. 8). Therefore, in Patent Document 1, an atmospheric pressure sensor detects the atmospheric pressure, and then an atmospheric pressure correction amount map 92 is applied to the detected atmospheric pressure. This can calculate an atmospheric pressure correction amount. This atmospheric pressure correction amount is added to the standard injection timing by an adder 93, and thereby the final injection timing is calculated.
Although Patent Document 1 does not disclose, in the transient state such as in acceleration, the temperature within a cylinder is decreased by a decrease in the temperature of a gas remaining in the cylinder. This leads to a decrease in the stability of ignition. Therefore, at highlands and in the transient state, the pressure within a cylinder is significantly decreased and also the stability of ignition is significantly decreased (see highlands/transient of FIG. 8). Thus, even if the atmospheric pressure is the same, an optimum fuel injection timing is varied depending on the steady or transient state. Therefore, a configuration is known in which the fuel injection timing is calculated by performing processes shown in FIG. 7.
In a block diagram of FIG. 7, the fuel injection timing is calculated in consideration of the engine state (steady or transient state) along with the correction on the basis of the atmospheric pressure. More specifically, a standard injection timing map 94 is applied to the engine speed and fuel injection amount, and thereby the standard injection timing is calculated. Additionally, a transient injection timing map 95 is applied to the engine speed and fuel injection amount, and thereby a transient injection timing is calculated.
A switch 96 outputs the standard injection timing in a case of the steady state, and outputs the transient injection timing in a case of the transient state. In the block diagram of FIG. 7, an atmospheric pressure correction amount map 97 is applied to the atmospheric pressure, and thereby the atmospheric pressure correction amount is calculated. The atmospheric pressure correction amount is added to the outputted value of the switch 96 by an adder 98. In this manner, the final injection timing is calculated.